1. Field of the Invention The present invention relates to an image recording apparatus such as a copying machine or a printer in which a photosensitive recording medium is employed, and more particularly to such an image recording apparatus that employs a photosensitive recording medium which is used to form an output image sheet.
2. Discussion of the Related Art
Generally, an image recording apparatus which uses a photosensitive recording medium employs, for example, as disclosed in U.S. Pat. No. 4,903,070, the disclosure of which is herein incorporated by reference, an elongated web-like microcapsule sheet coated with a plurality of photo and pressure sensitive microcapsules, each microcapsule enveloping therein a chromogenic material and a photosensitive resin, and a developer sheet coated with a developing material which produces an output image upon reaction with the chromogenic material, as is well known in the art.
The image recording apparatus comprises means for receiving the elongated web-like microcapsule sheet wound around a cartridge shaft and retained in a cartridge, an exposing unit for exposing the microcapsule sheet disposed at an exposure table to form a latent image thereon, a developer sheet feeding unit for feeding a developer sheet from a developer sheet cassette which stores therein, for example, a stack of developer sheets toward an exposed microcapsule sheet, a pressure developing unit for pressurizing the exposed microcapsule sheet superposed with the developer sheet to thereby form an output image on the developer sheet, a separating unit for separating the exposed microcapsule sheet from the developer sheet, a taking-up unit for taking-up the separated microcapsule sheet, and a thermal fixing unit for fixing the output image on the developer sheet.
In this type of image recording apparatus, the elongated microcapsule sheet drawn out of the cartridge passes through the exposing unit, the pressure developing unit and the separating unit, and is taken-up by the taking-up unit. The developer sheet and superposed elongated microcapsule sheet containing the latent image are pressurized by the pressure developing unit, and are separated from each other by the separating unit and then the developer sheet is subjected to thermal fixing in the thermal fixing unit. At this time, the copying operation is completed.
However, upon completion of the above copying operation, the leading edge of an unexposed portion of the microcapsule sheet has passed through the pressure developing unit. If the next copying operation is immediately performed in the above mentioned situation, an unexposed portion of the microcapsule sheet, located between the trailing edge of the exposed area from the preceding copying operation (now located near the separating unit) and the leading edge of the next exposing area for the next copying operation (now located near the exposing unit), was not fully utilized, resulting in waste of photosensitive recording medium.
In order to prevent waste of the photosensitive recording sheet, U.S. Pat. No. 4,801,976, the disclosure of which is herein incorporated by reference, discloses a copying machine for copying an image on a photo-pressure sensitive recording sheet, which comprises an exposing unit for exposing the photo-pressure sensitive sheet placed at an exposure position to form a latent image thereon, a magnification detection unit for detecting the degree of magnification of the image exposed by the exposing unit, and an exposure area controlling unit for controlling a feeding unit in response to said detection unit, whereby the photo-pressure sensitive sheet is exposed by the exposing unit from a leading edge thereof.
However, in this type of conventional copying machine, while the leading edge of the photo-pressure sensitive recording sheet is being controlled to be located at the proper exposure position, depression of the copy start key starts a next copying operation on the photo-pressure sensitive recording sheet irrespective of the completion of the adjustment of the leading edge of the unexposed portion of the photo-pressure sensitive recording sheet to the exposure position. For the above mentioned reason, the adjustment of the leading edge of the photo-pressure sensitive recording sheet is stopped, and a next copying operation is performed prior to proper placement of the leading edge of the unexposed portion of the photosensitive recording sheet to the exposure position. Accordingly, an unexposed portion of the photo-pressure sensitive recording sheet is wasted.